Heavy transportation, agricultural and construction equipment frequently rely on large diesel engines for power. It is important that clean air be delivered to these engines for combustion. Generally, one type of air cleaner for this purpose utilizes coaxial primary and secondary air filters, wherein the secondary air filter is nested within the primary air filter. Air is drawn from the atmosphere, radially through the primary and secondary filters and into the cylindrical space within the secondary filter. The filtered air then passes to the engine for mixture with fuel in the combustion chamber of the engine.
In order to ensure proper filtering of combustion air, the primary and secondary air filters are sealed within a housing by an arrangement of radial and axial sealing elements and gaskets. In one prior art approach, sealing of the filters is accomplished by compressing the outlet end of the filter against the end wall of the housing and by providing a gasket between the end of the filter and the end wall of the housing. This is accomplished by, for example, utilizing a yoke assembly which cooperates with a threaded wing nut, the nut being used to compress the filters against the end wall of the housing to prevent leakage of air around the filter elements. In the past, various other latches and clamping devices have been used to effect a positive clean air seal with such filter assemblies.
Axial compression techniques for sealing require filters which are constructed so as not to collapse under compression. In prior art devices, this required the use of relatively heavy gauge steel housings to withstand the compressive pressures. Because both the filter housing and filter must be strong and rigid when using such techniques, the development of low cost., light weight filters in housings has been hampered. Accordingly, relatively expensive housings, as well as relatively expensive molding processes were utilized which, of course, increased the costs of the filter assemblies. Since filter assemblies are disposable after use, the expensive investment in these materials and processes does not result in extended filter life, but rather simply increases the cost of filters. The effect of filter expense is continuous since the expense of filters discourages their timely replacement which, of course, results in decreased engine life which, in turn, results in equipment being retired or overhauled early, an undesirable consequence in and of itself.
U.S. Pat. No. 4,720,292 to Engel et al. addresses the problem with relatively soft, radially directed end seals. In practice, the arrangement disclosed in this patent requires a plastic clip placed in the housing to push the filter inward for a tighter seal. Since the end cap of the Engel et al. patent is polyurethane, the end cap is relatively soft, resulting in a relatively weak, compressible seal which feels to the installer to be less effective than it might be.
In view of these considerations, there is a need for a new and improved sealing end cap arrangement which still allows use of relatively inexpensive filter housings and retaining structures while providing an effective seal which will last at least as long as the filter material.